Athermal AWG and AWG with low power consumption using groove of changeable width

ABSTRACT

Optical integrated circuits are disclosed having a gap traversing the lens or the waveguide grating and an actuator that controllably positions the optical integrated circuit on each side of the gap. As a result, the thermal sensitivity of the optical integrated circuits, for example, arrayed waveguide gratings, is mitigated. Also disclosed are methods for fabricating optical integrated circuits employing the gap and actuator.

This patent application is a continuation of application Ser. No.10/100,958 filed on Mar. 18, 2002, now U.S. Pat. No. 6,738,545.

FIELD OF THE INVENTION

The present invention relates to the art of optical integrated circuitsand more particularly to apparatus and methods for providing arrayedwaveguides having a center wavelength that is independent oftemperature.

BACKGROUND OF THE INVENTION

Optical integrated circuits (OICs) come in many forms such as 1×Noptical splitters, optical switches, wavelength division multiplexers(WDMs), demultiplexers, optical add/drop multiplexers (OADMs), and thelike. Such OICs are employed in constructing optical networks in whichlight signals are transmitted between optical devices for carrying dataand other information. For instance, traditional signal exchanges withintelecommunications networks and data communications networks usingtransmission of electrical signals via electrically conductive lines arebeing replaced with optical fibers and circuits through which optical(e.g., light) signals are transmitted. Such optical signals may carrydata or other information through modulation techniques, fortransmission of such information through an optical network. Opticalcircuits allow branching, coupling, switching, separating, multiplexingand demultiplexing of optical signals without intermediatetransformation between optical and electrical media.

Such optical circuits include planar lightwave circuits (PLCs) havingoptical waveguides on flat substrates, which can be used for routingoptical signals from one of a number of input optical fibers to any oneof a number of output optical fibers or optical circuitry. PLCs make itpossible to achieve higher densities, greater production volume and morediverse functions than are available with fiber components throughemployment of manufacturing techniques typically associated with thesemiconductor industry. For instance, PLCs contain optical paths knownas waveguides formed on a silicon wafer substrate using lithographicprocessing, wherein the waveguides are made from transmissive media,which have a higher index of refraction than the chip substrate or theoutlying cladding layers in order to guide light along the optical path.By using advanced photolithographic and other processes, PLCs arefashioned to integrate multiple components and functionalities into asingle optical chip.

One important application of PLCs in particular and OICs generallyinvolves wavelength-division multiplexing (WDM) including densewavelength-division multiplexing (DWDM). DWDM allows optical signals ofdifferent wavelengths, each carrying separate information, to betransmitted via a single optical channel or fiber in an optical network.For example, early systems provided four different wavelengths separatedby 400 GHz, wherein each wavelength transferred data at 2.5 Gbits persecond. Current multiplexed optical systems employ as many as 160wavelengths on each optical fiber.

In order to provide advanced multiplexing and demultiplexing (e.g.,DWDM) and other functions in such networks, arrayed-waveguide gratings(AWGs) have been developed in the form of PLCs. Existing AWGs canprovide multiplexing or demultiplexing of up to 80 channels orwavelengths spaced as close as 50 GHz. As illustrated in FIG. 1, aconventional demultiplexing AWG 2 includes a single input port 3, andmultiple output ports 4. Multiple wavelength light is received at theinput port 3 (e.g., from an optical fiber in a network, not shown) andprovided to an input lens 5 via an input optical path or waveguide 6.

The input lens 5 spreads the multiple wavelength light into an array ofwaveguides 7, sometimes referred to a waveguide grating. Each of thewaveguides 7 has a different optical path length from the input lens 5to an output lens 8, resulting in a different phase tilt at the input tothe output lens 8 depending on wavelength. This phase tilt, in turn,affects how the light recombines in the output lens 8 throughconstructive interference. The output lens 8 thus provides differentwavelengths at the output ports 4 via individual output waveguides 9,whereby the AWG 2 can be employed in demultiplexing light signalsentering the input port 6 into two or more demultiplexed signals at theoutput port 4. The AWG 2 can alternatively be used to multiplex lightsignals from the ports 4 into a multiplexed signal having two or morewavelength components at the port 3.

One of the problems with optical integrated circuits, such as theconventional AWG 2 of FIG. 1 is temperature sensitivity. Since thewaveguide material usually has a temperature dependent refractive index,the channel wavelengths of multi/demultiplexer shift as the temperaturevaries. This shift is typically of the order of 0.01 nm/E C insilica-based devices and 0.1 nm/E C in InP based devices. Thiswavelength shift can result in a loss of signal and/or cross talk incommunication system(s) employing the AWG 2. As communication system(s)are designed with increasingly smaller channel spacing, even a smalltemperature dependent wavelength shift can have a significant effect onsystem performance. Presently, AWG=s must have active stabilization ofthe device operating temperature in order to perform acceptably. Thisstabilization is typically achieved by the addition of resistiveheaters, temperature sensors, active electronics, and in some cases alsothermo-electric coolers. Even though an AWG is a passive filter,currently it requires significant electronics and a few watts of powerto operate effectively.

Accordingly, there remains a need for better solutions to temperaturesensitivity in optical integrated circuits such as AWGs, which avoid ormitigate the performance reductions associated with conventional opticalintegrated circuits and provide for mitigation of active temperaturestabilization and its associated costs.

SUMMARY OF THE INVENTION

The following presents a simplified summary of the invention in order toprovide a basic understanding of some aspects of the invention. Thissummary is not an extensive overview of the invention. It is intended toneither identify key or critical elements of the invention nor delineatethe scope of the invention. Rather, the sole purpose of this summary isto present some concepts of the invention in a simplified form as aprelude to the more detailed description that is presented hereinafter.

The present invention provides athermal optical integrated circuits andmethods for athermalizing optical integrated circuits mitigating and/orovercoming the shortcomings associated with conventional opticalintegrated circuit(s) and other devices. The invention further comprisesmethods for fabricating OICs and for mitigating temperature sensitivityutilizing a groove and an actuator. Markedly lower power consumptionalso results from employing temperature responsive mechanical actuatorsin another aspect of the present invention.

According to an aspect of the present invention, an optical integratedcircuit is provided that contains a base containing a first region and asecond region separated by a hinge, and an AWG chip over the base, wherea groove traverses one or more of one of the lenses and the waveguidegrating, and an actuator connecting the first region and the secondregion of the base. The base and actuator have different thermalexpansion coefficients. The actuator expands and/or contracts withtemperature changes causing the first region and at least a portion ofthe AWG chip thereover to move with respect to the portion of the AWGchip over the second region. Thus, wavelength shift associated withwaveguide temperature dependent refractive index can be mitigated.

According to another aspect of the present invention, optical integratedcircuit is provided that contains an AWG chip with a groove traversingone or more of the lenses and the waveguide grating. The AWG chipcontains a first region and a second region connected by a hinge andseparated by the groove. An actuator connects the first region and thesecond region of the AWG chip. The AWG chip substrate and actuator havedifferent thermal expansion coefficients. The actuator expands and/orcontracts with temperature changes causing the first region of the AWGchip to move with respect to the second region. Thus, wavelength shiftassociated with waveguide temperature dependent refractive index can bemitigated.

Another aspect of the invention provides a methodology for fabricatingan OIC capable of mitigating wavelength shift associated with waveguidetemperature dependent refractive index. Fabrication of the OIC includesforming a groove in the AWG chip so that an actuator can induce relativemovement between different portions of the chip in response totemperature changes.

To the accomplishment of the foregoing and related ends, certainillustrative aspects of the invention are described herein in connectionwith the following description and the annexed drawings. These aspectsare indicative, however, of but a few of the various ways in which theprinciples of the invention may be employed and the present invention isintended to include all such aspects and their equivalents. Otheradvantages and novel features of the invention will become apparent fromthe following detailed description of the invention when considered inconjunction with the drawings.

BRIEF SUMMARY OF THE DRAWINGS

FIG. 1 is a schematic top plan view of a conventional AWGmultiplexer/demultiplexer device.

FIG. 2 is a schematic top plan view of a base or riser in accordancewith one aspect of the present invention.

FIG. 3 is a schematic top plan view of an OIC in accordance with oneaspect of the present invention.

FIG. 4 is a cross-sectional view of the OIC of FIG. 3.

FIG. 5 is a schematic top plan view of another base or riser inaccordance with one aspect of the present invention.

FIG. 6 is a schematic top plan view of another OIC in accordance withone aspect of the present invention.

FIG. 7 is a schematic top plan view of yet another base or riser inaccordance with one aspect of the present invention.

FIG. 8 is a schematic top plan view of yet another OIC in accordancewith one aspect of the present invention.

FIG. 9 is a schematic top plan view of still yet another base or riserin accordance with one aspect of the present invention.

FIG. 10 is a schematic top plan view of still yet another OIC inaccordance with one aspect of the present invention.

FIG. 11 is a schematic top plan view of another base or riser inaccordance with one aspect of the present invention.

FIG. 12 is a schematic top plan view of another OIC in accordance withone aspect of the present invention.

FIG. 13 is a schematic top plan view of an AWG chip in accordance withone aspect of the present invention.

FIG. 14 is a schematic top plan view of another AWG chip in accordancewith one aspect of the present invention.

FIG. 15 is a schematic top plan view of an OIC in accordance with oneaspect of the present invention.

FIG. 16 is a schematic top plan view of another OIC in accordance withone aspect of the present invention.

FIG. 17 is a schematic top plan view of yet another OIC in accordancewith one aspect of the present invention.

FIG. 18 is a schematic top plan view of still yet another OIC inaccordance with one aspect of the present invention.

FIG. 19 is a graph plotting change in CW (y axis) versus change intemperature (x axis) for a conventional AWG that is not temperaturestabilized and an AWG in accordance with one aspect of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The various aspects of the present invention will now be described withreference to the drawings, wherein like reference numerals are used torefer to like elements throughout. The invention provides for mitigationof temperature sensitivity of optical integrated circuits by employingmechanical beam steering.

The present invention provides athermal OICs and OICs with low powerconsumption by employing beam deflection, using an OIC or AWG having twoor more distinct regions or pieces that can move relative to oneanother. This relative movement causes shifts in the center wavelength(CW), or wavelength of peak transmission for a given channel, of the OICthat are proportional to the motion of the two pieces. The OIC isdesigned such that the degree of CW change caused by the motion of thetwo pieces is equal in magnitude and opposite in sign to the CW changeinherent in the OIC (as caused by expansion/contraction of the OIC anddependencies of waveguide refractive index upon temperature) then thedevice has approximately zero net dependence of CW upon temperature,having a center wavelength that is substantially independent oftemperature, and is thus termed athermal.

As the temperature of an OIC increases or decreases, the index ofrefraction of one or more region waveguide(s) may change. In order tocompensate for this temperature based index of refraction change, theactuator expands/contracts as a result of the temperature change,causing the edges of the AWG chip in the groove to move (eg., rotate).The movement (rotation) caused by temperature changes corresponds to orcompensates for the temperature-change induced wavelength shifts in thewaveguide(s) due to temperature dependent refractive index. As such,wavelength shift associated with waveguide temperature dependentrefractive index change can be mitigated. Thus, loss of signal and/orcross talk in communication system(s) employing the OIC can be reduced.

Generally speaking, an AWG chip is positioned over a base. The base hasa hinge separating and connecting a first region and a second region ofthe base. The hinge connects the first region and second region yetpermits the first region and second region of the base to move relativeto one another. Typically, the hinge is a relatively narrow strip of thebase (or AWG substrate as described below). An actuator is connected tothe first region and second region of the base, andexpansion/contraction of the actuator may induce movement of the firstand second regions about the hinge. The actuator and the base havedifferent thermal expansion coefficients. A groove or gap is formed inthe AWG chip in a position at least approximately over the hinge. Oneportion or piece of the AWG chip on one side of the groove is over andsupported by the first region of the base while the other portion orpiece of the AWG chip on the other side of the groove is over andsupported by the second region of the base. Thus, movement of the firstand second regions about the hinge induced by the expansion/contractionof the actuator causes the two portions or pieces of the AWG chip tomove relative to one another.

Alternatively, the actuator connects the two portions or pieces of theAWG chip and expansion/contraction of the actuator may induce movementof the two portions or pieces of the AWG chip relative one another. Theactuator and the AWG chip substrate have different thermal expansioncoefficients. The base is constructed in such a manner so as to permitsuch movement between portions or pieces of the AWG chip (such asdescribed above).

Still alternatively, the above described mechanism can be applied to astructure containing about half of the AWG chip, but equipped with amirror. In such a structure, a groove is formed by positioning thewaveguide grating or lens close to the mirror, but not directly affixedto the mirror (to permit movement). The actuator and the AWG chip/mirrorsubstrate have different thermal expansion coefficients.

Although AWG chips containing an waveguide grating are discussed atlength, the OIC may contain a Mach-Zehnder interferometer. In this case,the groove traverses the arms or waveguides of the Mach-Zehnder device.

The width of the groove in the AWG chip, or the width between the AWGchip and a mirror (hereinafter also referred to as a groove) issufficient to permit movement so as to shift the CW. In one embodiment,the width of groove is about 1 micron or more and about 50 microns orless. In another embodiment, the width of groove is about 3 microns ormore and about 30 microns or less. In yet another embodiment, the widthof groove is about 5 microns or more and about 25 microns or less. Instill yet another embodiment, the width of groove is about 7 microns ormore and about 20 microns or less. The AWG chip may contain more thanone groove. The groove or gap may be straight, curved, have a symmetricshape, or a asymmetric shape as it traverses the lens, waveguidegrating, or is adjacent a mirror. In embodiments where the groove isasymmetric, the width of the groove as it traverses the lens orwaveguide grating may vary yet remain within the width parametersdescribed above. At widths over 50 microns, insertion loss concernsstart to become significant.

The difference in thermal expansion coefficients between the actuatorand the base, between the actuator and the AWG chip substrate, orbetween actuator and the AWG chip/mirror substrate is sufficient toinduce relative movement of the two portions or pieces of the AWG chipby expansion/contraction of the actuator. In one embodiment, thedifference in thermal expansion coefficients (for example, between theactuator and the base) is at least about 25%. In another embodiment, thedifference in thermal expansion coefficients is at least about 100% (inother words the actuator can be at least twice the value of the base).In yet another embodiment, the difference in thermal expansioncoefficients is at least about 200% (in other words the actuator can beat least three times the value of the base).

In one embodiment, an athermal OIC contains an AWG chip mounted over abase or a riser with hinge positioned under the waveguide grating, suchas under the center portion of the waveguide grating. For example,referring to FIGS. 2 to 4, an example of such an OIC, and a method offabricating the OIC, is shown.

Specifically referring to FIG. 2, a base 10, sometimes referred to as ariser, is provided. The base 10 is configured to contain a hinge 14separating and connecting a first region 11 and a second region 13. Thebase is made of a material having a first thermal expansion coefficient.The base can be made of a metal, metal alloy, or hard plastic material.Examples of metals include one or more of aluminum, brass, bronze,chromium, copper, gold, iron, magnesium, nickel, palladium, platinum,silver, stainless steel, tin, titanium, tungsten, zinc, zirconium,Hastelloy®, Kovar®, Invar, Monel®, Inconel®, and the like.

An actuator 12 having a second thermal expansion coefficient, differentfrom the first thermal expansion coefficient of the base 10 is providedconnecting the first region 11 and the second region 13 of the base 10.The base can bend due to the hinge 14. That is, the first region 11 andthe second region 13 may rotate about the hinge 14 consistent with thearrows.

The actuator 12 can be made of one or more of a metal such as aluminum,brass, bronze, chromium, copper, gold, iron, magnesium, nickel,palladium, platinum, silver, stainless steel, tin, titanium, tungsten,zinc, zirconium, Hastelloy®, Kovar®, Invar, Monel®, Inconel®, a ceramicmaterial such as alumina or aluminum silicate, a polymeric material suchas silicone rubber or an elastomer, polycarbonates, polyolefins,polyamides, polyesters, liquid crystal polymers, polymer compositematerials (polymer combined with carbon fiber, graphite, or fiberglass),and the like. An example of a polymer composite is DuPont's Zytel®fiberglass reinforced Nylon. The actuator 12 may alternatively be amechanical assembly containing a number of different materials designedto have, as a whole, a specific thermal expansion coefficient (differentfrom that of the base 10).

The mechanical actuator 12 may alternatively be a piezoelectric element,an electrostrictive actuator, solenoid, electric motor such as a servomotor, linear motor, or stepper motor, or resistively heated thermalexpanding member. When the actuator 12 is one of a piezoelectricelement, solenoid, electric motor, or resistively heated thermalexpanding member, one or more temperature sensors may be placed withinthe waveguide grating connected to a feedback loop that is connected tothe actuator (a controller and/or processor may be also included in thefeedback loop). Temperature changes detected by the sensor lead to asignal which is sent to the controller/processor that in turn leads tomechanical actuation of the actuator. In another embodiment, theactuator is described in U.S. Ser. No. 10/100,833 filed concurrentlyherewith entitled “Method and Apparatus Facilitating Mechanical BeamSteering for Optical Integrated Circuits” which incorporated herein byreference. In yet another embodiment, an actuator or block is describedin co-pending U.S. Ser. No. 09/999,692 filed Oct. 24, 2001, now U.S.Pat. No. 6,603,892, entitled “Mechanical Beam Steering for OpticalIntegrated Circuits” along with related concepts, which is incorporatedherein by reference.

Referring to FIG. 3, an AWG chip 16 is affixed to the base 10 by anysuitable means. For example, an adhesive such as an UV curable adhesivecan be positioned between the AWG chip 16 and the base 10. The AWG chip16 is shown having a substrate, an input waveguide, a first lens, asecond lens, a waveguide grating between the two lenses containing aplurality of waveguides, and output waveguides. The substrate of the AWGchip 16 can be made of one or more of silica, silicon, InP, GaAs, andthe like. The input waveguide, the waveguide grating, and the outputwaveguide can be independently made of one or more of lithium niobate(LiNbO3) or other inorganic crystals, doped silica, undoped silica,glass, thermo-optic polymers, electro-optic polymers, and semiconductorssuch as indium phosphide (InP). Cladding layers may surround the variouswaveguides. It is noted that the actuator 12 may be attached to the base10 before or after the AWG chip 16 is affixed to the base 10. Althoughnot shown, the AWG chip 16 and/or base 10 can be cut to minimize thelength of the groove 18; that is, to greatly increase the width ofgroove in locations where it does not traverse the waveguide grating (orlens as described below).

In this embodiment, the AWG chip 16 is positioned over the base so thatthe waveguide grating is directly above the hinge 14 of the base 10. Agap or groove 18 is formed in the AWG chip 16 traversing the waveguidegrating. The groove 18 goes all the way through the AWG chip 16vertically, and may or may not divide the AWG chip 16 into two distinctpieces. The AWG chip is diced in any suitable manner including using adicing saw, water jet cutting, chemical etching, laser-wafer-cutter,wire-saw, EDM, and the like. One portion of the AWG chip 16 on one sideof the groove 18 is supported by the first region 11 of the base 10while another portion of the AWG chip 16 on the other side of the groove18 is supported by the second region 13 of the base 10.

Referring to FIG. 4, a side view of the structure of FIG. 3 is shownalong the arrows in FIG. 3. The gap 18 is completely through the AWGchip 16 in a vertical orientation. The gap 18 is located at or near thecenter of the grating, or at or near a perpendicular angle to thewaveguides of the grating. Although the interior edges of the AWG chip16 within the groove 18 are shown as perpendicular to the surface ofbase 10, the groove 18 may optionally be formed so that it is at a smallangle to a line normal to the base surface in order to mitigate backreflection of light as the light crosses the groove 18. For example, thegroove 18 may be formed at an angle of about 5° or more and about 15° orless to a line normal to the base surface.

Within the gap or groove 18, a waveplate (not shown), such as a halfwaveplate, may be optionally formed. Additionally or alternatively, thegap or groove 18 may filled with an adhesive, gel, polymer or liquidhaving an index of refraction that substantially matches that of thewaveguides of the waveguide grating. The effect depends only weakly onthe refractive index of the index matching substance, so that tightcontrol of the substance's refractive index is not necessary. Stillalternatively, the interior facing edges of the AWG chip 16 (in thegroove 18) can be coated with an antireflection film and remain exposedto air.

As the temperature of the structure changes, the actuator 12 changeslength at a different rate than the base 10, due to differences in thecoefficients of thermal expansion. This causes a change in the anglebetween the two regions of the AWG (on either side of the groove 18),and causes a different phase delay for different waveguides in thewaveguide grating, and thus causes a shift in the CW of the device. Theactuator and base material size and shape are chosen such that the CWshift caused by the thermal expansion/contraction of the actuatorexactly balances the CW shift in the AWG due to change in temperature.As a result, the AWG CW is independent of temperature. The amount ofpre-bias put on the actuator also can be tuned to tune in the correct CWfor the AWG.

In another embodiment, an athermal OIC contains an AWG chip mounted overa base or a riser with hinge positioned under one of the lenses. Forexample, referring to FIGS. 5 to 8, examples of such OICs, and methodsof fabricating the OICs, are shown.

Specifically referring to FIG. 5, a base 20 is provided. The base 20 isconfigured to contain a hinge 24 separating and connecting a firstregion 21 and a second region 23. The base is made of a material havinga first thermal expansion coefficient. An actuator 22 having a secondthermal expansion coefficient, different from the first thermalexpansion coefficient of the base 20 is provided connecting the firstregion 21 and the second region 23 of the base 20. The base can bend dueto the hinge 24. That is, the first region 21 and the second region 23may rotate about the hinge 24 consistent with the arrows.

Referring to FIG. 6, an AWG chip 26 is affixed to the base 20 by anysuitable means. For example, an adhesive can be positioned between theAWG chip 26 and the base 20. The AWG chip 26 is shown having asubstrate, an input waveguide, a first lens, a second lens, a waveguidegrating between the two lenses containing a plurality of waveguides, andoutput waveguides. The base 20, substrate, actuator 22, and waveguidescan be made of any of the materials for these features described inconnection with FIGS. 2 and 3. It is noted that the actuator 22 may beattached to the base 20 before or after the AWG chip 26 is affixed tothe base 20.

In this embodiment, the AWG chip 26 is positioned over the base so thatone of the lenses is directly above the hinge 24 of the base 20. A gapor groove 28 is formed in the AWG chip 26 traversing the lens. Thegroove 28 may be formed in the middle of the lens, near the input/outputwaveguides side of the lens, or near the waveguide grating side of thelens. The groove 28 goes all the way through the AWG chip 26 vertically,and may or may not divide the AWG chip 26 into two distinct pieces. Thegroove is formed in any suitable manner including using a dicing saw,water jet cutting, chemical etching, laser-wafer-cutter, wire-saw, EDM,and the like. One portion of the AWG chip 26 on one side of the groove28 is supported by the first region 21 of the base 20 while anotherportion of the AWG chip 26 (containing the waveguide grating) on theother side of the groove 28 is supported by the second region 23 of thebase 20.

The gap or groove 28 may be optionally filled with an adhesive, gel,polymer or liquid having an index of refraction that substantiallymatches that of the lens. The effect depends only weakly on therefractive index of the index matching substance, so that tight controlof the substance's refractive index is not necessary. Alternatively, theinterior facing edges of the AWG chip 26 (in the groove 28) can beoptionally coated with an antireflection film and remain exposed to air.

As the temperature of the structure changes, the actuator 22 changeslength at a different rate than the base 20, due to differences in thecoefficients of thermal expansion. This causes a change in the anglebetween the two regions of the AWG (on either side of the groove 28), inparticular between two regions of the lens traversed by the groove 28,and deflection of part of the lens and the input (our output) waveguideto move the waveguide relative to the focus point of the light, thusshifting which wavelengths are focused into the waveguide grating, andthus causes a shift in the CW of the device. The actuator and basematerial size and shape are chosen such that the CW shift caused by thethermal expansion/contraction of the actuator exactly balances the CWshift in the AWG due to change in temperature. As a result, the AWG CWis independent of temperature. The amount of pre-bias put on theactuator also can be tuned to tune in the correct CW for the AWG.

Specifically referring to FIG. 7, a base 30 is provided. The base 30 isconfigured to contain a hinge 34 separating and connecting a firstregion 31 and a second region 33. The base is made of a material havinga first thermal expansion coefficient. An actuator 32 having a secondthermal expansion coefficient, different from the first thermalexpansion coefficient of the base 30 is provided connecting the firstregion 31 and the second region 33 of the base 30. The base can bend dueto the hinge 34. That is, the first region 31 and the second region 33may rotate about the hinge 34 consistent with the arrows. In thisembodiment, the shape of the base 30 is tailored to the shape of the AWGchip 36 described below.

Referring to FIG. 8, an AWG chip 36 is affixed to the base 30 by anysuitable means. For example, an adhesive can be positioned between theAWG chip 36 and the base 30. The AWG chip 36 is tailored to the arrayedwaveguide grating thereon. The AWG chip 36 is shown having a substrate,an input waveguide, a first lens, a second lens, a waveguide gratingbetween the two lenses containing a plurality of waveguides, and outputwaveguides. The base 30, substrate, actuator 32, and waveguides can bemade of any of the materials for these features described in connectionwith FIGS. 2 and 3. It is noted that the actuator 32 may be attached tothe base 30 before or after the AWG chip 36 is affixed to the base 30.

In this embodiment, the AWG chip 36 is positioned over the base so thatone of the lenses is directly above the hinge 34 of the base 30. A gapor groove 38 is formed in the AWG chip 36 traversing the lens. Thegroove 38 goes all the way through the AWG chip 36 vertically, and mayor may not divide the AWG chip 36 into two distinct pieces. The grooveis formed in any suitable manner including using a dicing saw, water jetcutting, chemical etching, laser-wafer-cutter, wire-saw, EDM, and thelike. One portion of the AWG chip 36 on one side of the groove 38 issupported by the first region 31 of the base 30 while another portion ofthe AWG chip 36 (containing the waveguide grating) on the other side ofthe groove 38 is supported by the second region 33 of the base 30. Theshape of the AWG chip 36 may be tailored so that substrate that is notnear any one of the input/output waveguides, lenses, waveguide gratingis eliminated, and/or so as to allow proper space for the installationof the actuator. Notches, bosses, and the like can be formed tofacilitate attachment of the actuator. For example, AWG chip 36 of FIG.8 has a tailored shape whereas AWG chip 26 of FIG. 6 does not.

The gap or groove 38 may be optionally filled with an adhesive, gel,polymer or liquid having an index of refraction that substantiallymatches that of the lens. The effect depends only weakly on therefractive index of the index matching substance, so that tight controlof the substance's refractive index is not necessary. Alternatively, theinterior facing edges of the AWG chip 36 (in the groove 38) can beoptionally coated with an antireflection film and remain exposed to air.

As the temperature of the structure changes, the actuator 32 changeslength at a different rate than the base 30, due to differences in thecoefficients of thermal expansion. This causes a change in the anglebetween the two regions of the AWG (on either side of the groove 38), inparticular between two regions of the lens traversed by the groove 38,and deflection of part of the lens and the input (our output) waveguideto move the waveguide relative to the focus point of the light, thusshifting which wavelengths are focused into the waveguide grating, andthus causes a shift in the CW of the device. The actuator and basematerial size and shape are chosen such that the CW shift caused by thethermal expansion/contraction of the actuator exactly balances the CWshift in the AWG due to change in temperature. As a result, the AWG CWis independent of temperature. The amount of pre-bias put on theactuator also can be tuned to tune in the correct CW for the AWG.

In yet another embodiment, an athermal OIC contains an AWG chip mountedover a base or a riser with hinge positioned under the waveguide gratingand a mirror. For example, referring to FIGS. 9 and 10, an example ofsuch an OIC, and a method of fabricating the OIC, is shown.

Specifically referring to FIG. 9, a base 40 is provided. The base 40 isconfigured to contain a hinge 44 separating and connecting a firstregion 41 and a second region 43. An actuator 42 having a second thermalexpansion coefficient, different from the first thermal expansioncoefficient of the base 40 is provided connecting the first region 41and the second region 43 of the base 40. The base can bend due to thehinge 44. That is, the first region 41 and the second region 43 mayrotate about the hinge 44 consistent with the arrows.

Referring to FIG. 10, an AWG chip 52 and a mirror 47 are affixed to thebase 40 by any suitable means. For example, an adhesive can bepositioned between the AWG chip 52 or mirror 47 and the base 40. The AWGchip 52 is shown having a substrate, an input waveguide 46, a lens 50, awaveguide grating between the lens and the mirror 47 containing aplurality of waveguides, and output waveguides 54. The base 40,substrate, actuator 42, and waveguides can be made of any of thematerials for these features described in connection with FIGS. 2 and 3.The AWG chip 52 and mirror 47 are positioned so that a groove or gap 48exists therebetween. The mirror 47 functions to reflect back light fromthe waveguide grating into the waveguide grating. It is noted that theactuator 42 may be attached to the base 40 before or after the AWG chip52 is affixed to the base 40.

In this embodiment, the AWG chip 52 and mirror 47 are positioned overthe base 40 so that the waveguide grating and mirror 47 are directlyabove the hinge 44 of the base 40. A gap or groove 48 traverses thewaveguide grating. The groove 48 completely separates the AWG chip 52from the mirror 47. The AWG chip 52 is on one side of the groove 48 andis supported by the first region 41 of the base 40 while the mirror 47is on the other side of the groove 48 and is supported by the secondregion 43 of the base 40.

Within the gap or groove 48, a waveplate (not shown), such as a quarterwaveplate, may be optionally formed. Additionally or alternatively, thegap or groove 48 may filled with an adhesive, gel, polymer or liquidhaving an index of refraction that substantially matches that of thewaveguides of the waveguide grating. The effect depends only weakly onthe refractive index of the index matching substance, so that tightcontrol of the substance's refractive index is not necessary. Stillalternatively, the interior facing edge of the AWG chip 46 (in thegroove 48) can be polished or coated with an antireflection film andremain exposed to air.

As the temperature of the structure changes, the actuator 42 changeslength at a different rate than the base 40, due to differences in thecoefficients of thermal expansion. This causes a change in the anglebetween the AWG and the mirror 47, and causes a different phase delayfor different waveguides in the waveguide grating, and thus causes ashift in the CW of the device. In particular, the angle at which themirror is attached is used to select the AWG CW, and the degree ofrotation of the mirror provided by the actuator as a function oftemperature is used to cancel the AWG=s thermal response. The actuatorand base material size and shape are chosen such that the CW shiftcaused by the thermal expansion/contraction of the actuator exactlybalances the CW shift in the AWG due to change in temperature. As aresult, the AWG CW is independent of temperature. The amount of pre-biasput on the actuator also can be tuned to tune in the correct CW for theAWG.

In still yet another embodiment, an athermal OIC contains an AWG chipmounted over a base or a riser with hinge positioned under a lens and amirror. For example, referring to FIGS. 11 and 12, an example of such anOIC, and a method of fabricating the OIC, is shown.

Specifically referring to FIG. 11, a base 60 is provided. The base 60 isconfigured to contain a hinge 64 separating and connecting a firstregion 61 and a second region 63. An actuator 62 having a second thermalexpansion coefficient, different from the first thermal expansioncoefficient of the base 60 is provided connecting the first region 61and the second region 63 of the base 60. The base can bend due to thehinge 64. That is, the first region 61 and the second region 63 mayrotate about the hinge 64 consistent with the arrows.

Referring to FIG. 12, an AWG chip 66 and a mirror 67 are affixed to thebase 60 by any suitable means. For example, an adhesive can bepositioned between the AWG chip 66 or mirror 67 and the base 60. The AWGchip 66 is shown having a substrate, an input waveguide 72, a first lens70, a second lens 76 that is folded, a waveguide grating between thefirst lens 70 and the folded lens 76 containing a plurality ofwaveguides, and output waveguides 74. The base 60, substrate, actuator62, and waveguides can be made of any of the materials for thesefeatures described in connection with FIGS. 2 and 3. The AWG chip 66 andmirror 67 are positioned so that a groove or gap 68 exists therebetween.The mirror 67 functions to reflect back light from the folded lens 76into the folded lens 76 so that it may enter the waveguide grating. Itis noted that the actuator 62 may be attached to the base 60 before orafter the AWG chip 66 is affixed to the base 60.

In this embodiment, the AWG chip 66 and mirror 67 are positioned overthe base 60 so that the folded lens 76 and mirror 67 are directly abovethe hinge 64 of the base 60. A gap or groove 68 traverses the lens 76.The groove 68 completely separates the AWG chip 66 from the mirror 67.The AWG chip 66 is on one side of the groove 68 and is supported by thefirst region 61 of the base 60 while the mirror 67 is on the other sideof the groove 68 and is supported by the second region 63 of the base60.

The gap or groove 68 may be optionally polished, and optionally filledwith an adhesive, gel, polymer or liquid having an index of refractionthat substantially matches that of the waveguides of the waveguidegrating. The effect depends only weakly on the refractive index of theindex matching substance, so that tight control of the substance'srefractive index is not necessary. Alternatively, the interior facingedge of the AWG chip 66 (in the groove 68) can be optionally coated withan antireflection film and remain exposed to air.

As the temperature of the structure changes, the actuator 62 changeslength at a different rate than the base 60, due to differences in thecoefficients of thermal expansion. This causes a change in the anglebetween the lens 76 and the mirror 67, and deflection of part of thelens and the input (our output) waveguide to move the waveguide relativeto the focus point of the light, thus shifting which wavelengths arefocused into the waveguide grating, and thus causing a shift in the CWof the device. In particular, the angle at which the mirror is attachedis used to select the AWG CW, and the degree of rotation of the mirrorprovided by the actuator as a function of temperature is used to cancelthe AWG=s thermal response. The actuator and base material size andshape are chosen such that the CW shift caused by the thermalexpansion/contraction of the actuator exactly balances the CW shift inthe AWG due to change in temperature. As a result, the AWG CW isindependent of temperature.

The groove or gap may be formed in the AWG chip before or after mountingthe AWG chip on the base. Referring to FIG. 13, an AWG chip 86 suitablefor mounting on the base of FIG. 2 is shown. The AWG chip 86 is shownhaving a substrate, an input waveguide, a first lens, a second lens, awaveguide grating between the two lenses containing a plurality ofwaveguides, and output waveguides. A gap or groove 88 is formed in theAWG chip 86 traversing the waveguide grating, but not the entire chip.The AWG chip 86 is positioned over the base so that the waveguidegrating is directly above the hinge 14 (referring to FIG. 2) of the base10. If not already formed, a gap or groove 88 is formed in the AWG chip86 traversing the waveguide grating, but not the entire chip. The groove88 goes all the way through the AWG chip 86 vertically, but does notdivide the AWG chip 86 into two distinct pieces. The groove 88 is formedin any suitable manner including wet etching or RIE. One portion 87 ofthe AWG chip 86 on one side of the groove 88 is supported by the firstregion 11 of the base 10 while another portion 89 of the AWG chip 86 onthe other side of the groove 88 is supported by the second region 13 ofthe base 10.

The AWG chip 86 and base (underneath the chip) are then simultaneouslycut in any suitable manner, such as using a waterjet, wire saw, laser,and the like, to provide a structure similar to FIG. 3 except that theAWG chip 86 substantially superimposes the base. The cutting tailors theshape of the structure around the functional features of the AWG chip 86and in particular near the groove 88 so that the groove 88 separates theAWG chip 86 into two distinct pieces and the portions of the AWG chip 86above and below the groove 88 no longer hold the chip in a single piece.An actuator is then added connecting the two regions of the base or twopieces of the chip.

Within the gap or groove 88, a waveplate (not shown), such as a halfwaveplate, may be optionally formed. Additionally or alternatively, thegap or groove 88 may filled with an adhesive, gel, polymer or liquidhaving an index of refraction that substantially matches that of thewaveguides of the waveguide grating.

Referring to FIG. 14, an AWG chip 96 suitable for mounting on the baseof FIG. 7 is shown. The AWG chip 96 is shown having a substrate, aninput waveguide, a first lens, a second lens, a waveguide gratingbetween the two lenses containing a plurality of waveguides, and outputwaveguides.

In this embodiment, the AWG chip 96 is positioned over the base so thatone of the lenses is directly above the hinge 24 of the base 20(referring to FIG. 5). A gap or groove 98 is formed in the AWG chip 96traversing the lens before or after attaching the chip to the base. Thegroove 98 goes all the way through the AWG chip 96 vertically, but doesnot divide the AWG chip 96 into two distinct pieces. The groove 98 isformed in any suitable manner. One portion 97 of the AWG chip 96 on oneside of the groove 98 is supported by the first region 21 of the base 20while another portion 99 of the AWG chip 96 (containing the waveguidegrating) on the other side of the groove 98 is supported by the secondregion 23 of the base 20.

The AWG chip 96 and base (underneath the chip) are then simultaneouslycut in any suitable manner, such as using a waterjet, wire saw, laser,and the like, to provide a structure similar to FIG. 8 except that theAWG chip 96 substantially superimposes the base. The cutting tailors theshape of the structure around the functional features of the AWG chip 96and in particular near the groove 98 so that the groove 88 separates theAWG chip 96 into two distinct pieces and the portions of the AWG chip 96above and below the groove 88 no longer hold the chip in a single piece.An actuator is then added connecting the two regions of the base or twopieces of the chip.

The gap or groove 98 may filled with an adhesive, gel, polymer or liquidhaving an index of refraction that substantially matches that of thelens. Alternatively, the interior facing edges of the AWG chip 96 (inthe groove 98) can be coated with an antireflection film and remainexposed to air.

Although FIGS. 2 to 8 show AWG chips with a groove that completelyseparates the AWG chip into two pieces, the groove may alternativelyseparate the AWG chip into two regions. In another general embodiment,an AWG chip may be provided with a hinge, a gap or groove forming tworegions in the AWG chip, and an actuator connecting the two regions ofthe AWG chip separated and connected by the hinge, and optionallyaffixed to a conventional base or a base as described in one or more ofFIGS. 2, 5, 7, 9, and 11. If a base is employed, the base must allow formovement of the AWG chip induced by the actuator about the hinge. Sincethe OIC chip is not in two distinct pieces, a base is not necessary.

Referring to FIG. 15, an AWG chip 110 is shown having a substrate, aninput waveguide, a first lens, a second lens, a waveguide gratingbetween the two lenses containing a plurality of waveguides, and outputwaveguides. An actuator 112 connects two regions of the chip, divided bya groove 116. The AWG chip 110 contains a hinge 114. The substrate,actuator 112, and waveguides can be made of any of the materials forthese features described in connection with FIGS. 2 and 3.

The gap or groove 116 is formed in the AWG chip 110 traversing one ormore of the lenses. The groove 116 goes all the way through the AWG chip110 vertically. The groove 116 is formed in any suitable mannerincluding using a dicing saw, water jet cutting, chemical etching,laser-wafer-cutter, wire-saw, EDM, and the like. In this embodiment,chemical etching such as reactive ion etching (RIE) is preferred.Although not shown, the groove 116 may traverse the waveguide gratinginstead of the lens, and the hinge 114 would be positioned visuallyabove the waveguide grating.

Within the gap or groove 116, a waveplate (not shown), such as a halfwaveplate, may be optionally formed, particularly when the groovetraverses the waveguide grating. Additionally or alternatively, the gapor groove 116 may filled with an adhesive, gel, polymer or liquid havingan index of refraction that substantially matches that of the lens.Still alternatively, the interior facing edges of the AWG chip 110 (inthe groove 116) can be coated with an antireflection film and remainexposed to air.

As the temperature of the structure changes, the actuator 112 changeslength at a different rate than the substrate of the AWG chip 110, dueto differences in the coefficients of thermal expansion. This causes achange in the angle between the two regions of the AWG (on either sideof the groove 116), in particular between two regions of the lenstraversed by the groove 116, and deflection of part of the lens and theinput (our output) waveguide to move the waveguide relative to the focuspoint of the light, thus shifting which wavelengths are focused into thewaveguide grating, and thus causes a shift in the CW of the device. Theactuator and base material size and shape are chosen such that the CWshift caused by the thermal expansion/contraction of the actuatorexactly balances the CW shift in the AWG due to change in temperature.As a result, the AWG CW is independent of temperature. The amount ofpre-bias put on the actuator also can be tuned to tune in the correct CWfor the AWG.

Referring to FIG. 16, another embodiment of an AWG chip 120 is shownhaving a substrate, an input waveguide, a first lens, a second lens, awaveguide grating between the two lenses containing a plurality ofwaveguides, and output waveguides. An actuator 122 connects two regionsof the chip, divided by a groove 126. The AWG chip 120 contains a hinge124. The substrate, actuator 122, and waveguides can be made of any ofthe materials for these features described in connection with FIGS. 2and 3.

The gap or groove 126 is formed in the AWG chip 120 traversing one ormore of the lenses. The groove 126 goes all the way through the AWG chip120 vertically. The groove 126 is formed in any suitable mannerincluding using a dicing saw, water jet cutting, chemical etching,laser-wafer-cutter, wire-saw, EDM, and the like. In this embodiment,chemical etching such as reactive ion etching (RIE) is preferred.Although not shown, the groove 126 may traverse the waveguide gratinginstead of the lens, and the hinge 124 would be positioned visuallyabove the waveguide grating.

Within the gap or groove 126, a waveplate (not shown), such as a halfwaveplate, may be optionally formed, particularly when the groovetraverses the waveguide grating. Additionally or alternatively, the gapor groove 126 may filled with an adhesive, gel, polymer or liquid havingan index of refraction that substantially matches that of the lens.Still alternatively, the interior facing edges of the AWG chip 120 (inthe groove 126) can be coated with an antireflection film and remainexposed to air.

As the temperature of the structure changes, the actuator 122 changeslength at a different rate than the substrate of the AWG chip 120, dueto differences in the coefficients of thermal expansion. This causes achange in the angle between the two regions of the AWG (on either sideof the groove 126), in particular between two regions of the lenstraversed by the groove 126, and deflection of part of the lens and theinput (our output) waveguide to move the waveguide relative to the focuspoint of the light, thus shifting which wavelengths are focused into thewaveguide grating, and thus causes a shift in the CW of the device. Theactuator and base material size and shape are chosen such that the CWshift caused by the thermal expansion/contraction of the actuatorexactly balances the CW shift in the AWG due to change in temperature.As a result, the AWG CW is independent of temperature. The amount ofpre-bias put on the actuator also can be tuned to tune in the correct CWfor the AWG.

Referring to FIG. 17, yet another embodiment of an AWG chip 130 is shownhaving a substrate, an input waveguide, a first lens, a second lens, awaveguide grating between the two lenses containing a plurality ofwaveguides, and output waveguides. An actuator 132 connects two regionsof the chip, divided by a groove 136. The AWG chip 130 contains twohinges 134. The substrate, actuator 132, and waveguides can be made ofany of the materials for these features described in connection withFIGS. 2 and 3.

The gap or groove 136 is formed in the AWG chip 130 traversing one ormore of the lenses. The groove 136 goes all the way through the AWG chip130 vertically. The groove 136 is formed in any suitable mannerincluding using a dicing saw, water jet cutting, chemical etching,laser-wafer-cutter, wire-saw, EDM, and the like. In this embodiment,chemical etching such as reactive ion etching (RIE) is preferred.Although not shown, the groove 136 may traverse the waveguide gratinginstead of the lens, and the hinges 134 would be positioned visuallyabove and below the waveguide grating.

Within the gap or groove 136, a waveplate (not shown), such as a halfwaveplate, may be optionally formed, particularly when the groovetraverses the waveguide grating. Additionally or alternatively, the gapor groove 136 may filled with an adhesive, gel, polymer or liquid havingan index of refraction that substantially matches that of the lens.Still alternatively, the interior facing edges of the AWG chip 130 (inthe groove 136) can be coated with an antireflection film and remainexposed to air.

As the temperature of the structure changes, the actuator 132 changeslength at a different rate than the substrate of the AWG chip 130, dueto differences in the coefficients of thermal expansion. This causes achange in the angle between the two regions of the AWG (on either sideof the groove 136), in particular between two regions of the lenstraversed by the groove 136, and deflection of part of the lens and theinput (our output) waveguide to move the waveguide relative to the focuspoint of the light, thus shifting which wavelengths are focused into thewaveguide grating, and thus causes a shift in the CW of the device. Theactuator and base material size and shape are chosen such that the CWshift caused by the thermal expansion/contraction of the actuatorexactly balances the CW shift in the AWG due to change in temperature.As a result, the AWG CW is independent of temperature. The amount ofpre-bias put on the actuator also can be tuned to tune in the correct CWfor the AWG.

Referring to FIG. 18, yet another embodiment of an AWG chip 140 is shownhaving a substrate, an input waveguide, a first lens, a second lens, awaveguide grating between the two lenses containing a plurality ofwaveguides, and output waveguides. An actuator 142 connects two regionsof the chip, divided by a groove 146. The AWG chip 140 contains twohinges 144. The substrate, actuator 142, and waveguides can be made ofany of the materials for these features described in connection withFIGS. 2 and 3.

The gap or groove 146 is formed in the AWG chip 140 traversing one ormore of the lenses. The groove 146 goes all the way through the AWG chip130 vertically. The groove 146 is formed in any suitable mannerincluding using a dicing saw, water jet cutting, chemical etching,laser-wafer-cutter, wire-saw, EDM, and the like. In this embodiment,chemical etching such as reactive ion etching (RIE) is preferred.Although not shown, the groove 146 may traverse the waveguide gratinginstead of the lens, and the hinges 144 would be positioned visuallyabove and below the waveguide grating.

Within the gap or groove 146, a waveplate (not shown), such as a halfwaveplate, may be optionally formed, particularly when the groovetraverses the waveguide grating. Additionally or alternatively, the gapor groove 136 may filled with an adhesive, gel, polymer or liquid havingan index of refraction that substantially matches that of the lens.Still alternatively, the interior facing edges of the AWG chip 140 (inthe groove 146) can be coated with an antireflection film and remainexposed to air.

As the temperature of the structure changes, the actuator 142 changeslength at a different rate than the substrate of the AWG chip 140, dueto differences in the coefficients of thermal expansion. This causes achange in the angle between the two regions of the AWG (on either sideof the groove 146), in particular between two regions of the lenstraversed by the groove 146, and deflection of part of the lens and theinput (our output) waveguide to move the waveguide relative to the focuspoint of the light thus shifting which wavelengths are focused into thewaveguide grating, and thus causes a shift in the CW of the device. Theactuator and base material size and shape are chosen such that the CWshift caused by the thermal expansion/contraction of the actuatorexactly balances the CW shift in the AWG due to change in temperature.As a result, the AWG CW is independent of temperature. The amount ofpre-bias put on the actuator also can be tuned to tune in the correct CWfor the AWG.

In some embodiments of FIGS. 15 to 18, when a polymer occupies thegroove traversing a lens or waveguide grating (or between a mirror andan AWG chip), if the polymer has a desired coefficient of thermalexpansion, that is different from the coefficient of thermal expansionof the AWG chip 110 substrate, the polymer may function as an actuator.

Referring to FIG. 19, a graph showing the different CW changes/responsesto temperature for a conventional AWG that is not temperature stabilizedand an athermal AWG made in accordance with the present invention. Asthe graph indicates, as the temperature increases, the CW of theconventional AWG increasingly changes. On the contrary, as thetemperature increases, the CW of the athermal AWG made in accordancewith the present invention remains substantially constant.

Although the invention has been shown and described with respect tocertain illustrated implementations, it will be appreciated thatequivalent alterations and modifications will occur to others skilled inthe art upon the reading and understanding of this specification and theannexed drawings. In particular regard to the various functionsperformed by the above described components (assemblies, devices,systems, etc.), the terms (including a reference to a “means”) used todescribe such components are intended to correspond, unless otherwiseindicated, to any component which performs the specified function of thedescribed component (e.g., that is functionally equivalent), even thoughnot structurally equivalent to the disclosed structure, which performsthe function in the herein illustrated exemplary aspects of theinvention. In this regard, it will also be recognized that the inventionincludes a system as well as a computer-readable medium havingcomputer-executable instructions for performing the acts and/or eventsof the various methods of the invention.

In addition, while a particular feature of the invention may have beendisclosed with respect to only one of several implementations, suchfeature may be combined with one or more other features of the otherimplementations as may be desired and advantageous for any given orparticular application. Furthermore, to the extent that the terms“includes”, “including”, “with”, “has”, “having”, and variants thereofare used in either the detailed description or the claims, these termsare intended to be inclusive in a manner similar to the term“comprising.”

1. An athermalized optical integrated circuit, comprising: a baseconsisting essentially of one piece and having a first thermal expansioncoefficient, the base comprising a first region, a second region, and ahinge region, the first region and the second region separated by thehinge region; an arrayed waveguide chip supported by the base, thearrayed waveguide chip comprising a substrate, a lens, a waveguidegrating optically coupled to the lens, and a groove traversing one ofthe lens and the waveguide grating; and an actuator having a secondthermal expansion coefficient, the actuator connecting the first regionand the second region of the base, the actuator operative to move thefirst region of the base relative to the second region of the base inresponse to a temperature change, wherein the second thermal expansioncoefficient is different from the first thermal expansion coefficient.2. The athermalized optical integrated circuit of claim 1, wherein thesecond thermal expansion coefficient is less than the first thermalexpansion coefficient.
 3. The athermalized optical integrated circuit ofclaim 1, wherein the second thermal expansion coefficient is greaterthan the first thermal expansion coefficient.
 4. The athermalizedoptical integrated circuit of claim 1, wherein the actuator is one of apiezoelectric element, an electrostrictive actuator, a solenoid, and anelectric motor.
 5. The athermalized optical integrated circuit of claim1, wherein the groove traverses the waveguide grating.
 6. Theathermalized optical integrated circuit of claim 5, wherein the groovecomprises a waveplate.
 7. The athermalized optical integrated circuit ofclaim 1, wherein the groove traverses the lens.
 8. The athermalizedoptical integrated circuit of claim 1, wherein the groove has a width isabout 1 micron or more and about 50 microns or less.
 9. The athermalizedoptical integrated circuit of claim 1, wherein the groove completelytraverses the arrayed waveguide chip thereby forming a first piece ofthe arrayed waveguide chip and a second piece of the arrayed waveguidechip, the first piece of the arrayed waveguide chip supported by thefirst region of the base and the second piece of the arrayed waveguidechip supported by the second region.
 10. The athermalized opticalintegrated circuit of claim 1, wherein the arrayed waveguide chipcomprises at least one input waveguide optically coupled to a firstlens, at least one output waveguide optically coupled to a second lens,the waveguide grating optically coupled to the first lens and the secondlens, and the groove traverses one of the first lens, the second lens,and the waveguide grating.
 11. The athermalized optical integratedcircuit of claim 1, wherein the arrayed waveguide chip further comprisesa mirror, and the groove traverses a space between the mirror and one ofthe lens and the waveguide grating.
 12. An athermalized opticalintegrated circuit, comprising: an arrayed waveguide chip comprising asubstrate consisting essentially of one piece and, a lens, a waveguidegrating optically coupled to the lens, and a groove traversing one ofthe lens and the waveguide grating, the substrate having a first thermalexpansion coefficient, the substrate of the arrayed waveguide chipcomprising a first region, a second region, and a hinge region, thefirst region and the second region separated by the hinge region; anactuator having a second thermal expansion coefficient, the actuatorconnecting the first region and the second region of the arrayedwaveguide chip, the actuator operative to rotate the first region of thearrayed waveguide chip about the second region of the arrayed waveguidechip in response to a temperature change; and the arrayed waveguide chipbeing positioned over a base having a third thermal expansioncoefficient, the base comprising a first region and a second regionseparated by a hinge, wherein the second thermal expansion coefficientis different from the first thermal expansion coefficient.
 13. Theathermalized optical integrated circuit of claim 12, wherein thedifference between the second thermal expansion coefficient and thefirst thermal expansion coefficient is at least 100%.
 14. Theathermalized optical integrated circuit of claim 12, wherein the groovehas a width is about 3 microns or more and about 30 microns or less. 15.The athermalized optical integrated circuit of claim 12, wherein thearrayed waveguide chip comprises at least one input waveguide opticallycoupled to a first lens, at least one output waveguide optically coupledto a second lens, the waveguide grating optically coupled to the firstlens and the second lens, and the groove traverses one of the firstlens, the second lens, and the waveguide grating.
 16. The athermalizedoptical integrated circuit of claim 12, wherein the second thermalexpansion coefficient is less than the first thermal expansioncoefficient.
 17. A method of making an athermalized optical integratedcircuit, comprising: providing a base consisting essentially of onepiece and having a first thermal expansion coefficient, the base shapedto comprise a first region, a second region, and a hinge region, thefirst region and the second region separated by the hinge region;attaching an arrayed waveguide chip to the base, the arrayed waveguidechip comprising a substrate, a lens, and a waveguide grating opticallycoupled to the lens; forming a groove in the arrayed waveguide chip, thegroove traversing one of the lens and the waveguide grating; andattaching an actuator having a second thermal expansion coefficient tothe base, the actuator connecting the first region and the second regionof the base, wherein the second thermal expansion coefficient isdifferent from the first thermal expansion coefficient, the actuatoroperative to rotate the first region of the base about the second regionof the base in response to a temperature change.
 18. The method of claim17, wherein forming the groove comprises one of a dicing saw, a waterjet cutter, chemical etching, a laser-wafer-cutter, and a wire-saw. 19.A method of making an athermalized optical integrated circuit,comprising: providing an arrayed waveguide chip, the arrayed waveguidechip comprising a substrate consisting essentially of one piece, a lens,and a waveguide grating optically coupled to the lens, the substratehaving a first thermal expansion coefficient; shaping the substrate ofthe arrayed waveguide chip to comprise a first region and a secondregion separated by a groove and connected by a hinge region, thesubstrate remaining in one piece; and attaching an actuator having asecond thermal expansion coefficient to the arrayed waveguide chip, theactuator connecting the first region and the second region of thearrayed waveguide chip, wherein the second thermal expansion coefficientis different from the first thermal expansion coefficient, the groovetraversing one of the lens and the waveguide grating, the actuatoroperative to move the first region of the arrayed waveguide chiprelative to the second region of the arrayed waveguide chip in responseto a temperature change.
 20. The method of claim 19, wherein forming thegroove comprises one of a dicing saw, a water jet cutter, chemicaletching, a laser-wafer-cutter, and a wire-saw.
 21. An athermalizedoptical integrated circuit, comprising: a base having a first thermalexpansion coefficient, the base comprising a first region and a secondregion separated by a hinge; an arrayed waveguide chip over the base,the arrayed waveguide chip comprising a lens, a waveguide gratingoptically coupled to the lens, and a groove traversing one of the lensand the waveguide grating, one of the lens and the waveguide grating ispositioned directly above the hinge of the base; and an actuator havinga second thermal expansion coefficient, the actuator connecting thefirst region and the second region of the base, the actuator operativeto move the first region of the base relative to the second region ofthe base in response to a temperature change, wherein the second thermalexpansion coefficient is different from the first thermal expansioncoefficient.
 22. An athermalized optical integrated circuit, comprising:a base having a first thermal expansion coefficient, the base comprisinga first region and a second region separated by a hinge; an arrayedwaveguide chip over the base, the arrayed waveguide chip comprising alens, a waveguide grating optically coupled to the lens, and a groovetraversing one of the lens and the waveguide grating, the groove ispositioned directly above the hinge of the base; and an actuator havinga second thermal expansion coefficient, the actuator connecting thefirst region and the second region of the base, the actuator operativeto move the first region of the base relative to the second region ofthe base in response to a temperature change, wherein the second thermalexpansion coefficient is different from the first thermal expansioncoefficient.